Method of identifying an extreme interaction pitch region, methods of designing mask patterns and manufacturing masks, device manufacturing methods and computer programs

• US 20060277522A1
• Filed: 08/14/2006
• Published: 12/07/2006
• Est. Priority Date: 04/24/2001
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Masktools B.V. (ASML Holding NV)
• Inventors: Chen, Jang Fung, Hsu, Duan-Fu Stephen, Shi, Xuelong
• Granted Patent: US 7,735,052 B2
• Time in Patent Office: Days
• US Class Current: 716/53
• CPC Class Codes: G03F 1/36 Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes
• CPC Class Codes: G03F 7/70125 Use of illumination settings tailored to particular mask patterns details of setting means G03F7/70091
• CPC Class Codes: G03F 7/70441 Optical proximity correction [OPC]

Abstract

Optical proximity effects (OPEs) are a well-known phenomenon in photolithography. OPEs result from the structural interaction between the main feature and neighboring features. It has been determined by the present inventors that such structural interactions not only affect the critical dimension of the main feature at the image plane, but also the process latitude of the main feature. Moreover, it has been determined that the variation of the critical dimension as well as the process latitude of the main feature is a direct consequence of light field interference between the main feature and the neighboring features. Depending on the phase of the field produced by the neighboring features, the main feature critical dimension and process latitude can be improved by constructive light field interference, or degraded by destructive light field interference. The phase of the field produced by the neighboring features is dependent on the pitch as well as the illumination angle. For a given illumination, the forbidden pitch region is the location where the field produced by the neighboring features interferes with the field of the main feature destructively. The present invention provides a method for determining and eliminating the forbidden pitch region for any feature size and illumination condition. Moreover, it provides a method for performing illumination design in order to suppress the forbidden pitch phenomena, and for optimal placement of scattering bar assist features.

Claims

1. A method of identifying an extreme interaction pitch region when designing a mask pattern for transferring a lithographic pattern onto a substrate by use of a lithographic apparatus, said method comprising the steps of:

(a) determining an illumination intensity for a first pitch and a first illumination angle,

(b) determining an illumination intensity for said first pitch and a second illumination angle, said second illumination angle being rotationally symmetric with respect to said first illumination angle,

(c) determining a total illumination intensity for said first pitch by combining the illumination intensity associated with said first illumination angle and said second illumination angle,

(d) determining the log-slope of said total illumination intensity, and

(e) identifying a pitch region containing said first pitch as an extreme interaction pitch region if the value of the derivative of the log-slope of said total illumination intensity with respect to pitch is approximately equal to zero.

2-21. -21. (canceled)